FIG. 1 is a side-sectional view illustrating a part of a usual linear compressor, and FIG. 2 is a disassembled perspective view illustrating a frame and a motor cover of the conventional linear compressor.
Referring to FIG. 1, in the usual linear compressor, one end of a piston 4 is inserted into a cylinder 2, for forming a compression space P, and a linear motor 10 including an inner stator 12, an outer stator 14 and a permanent magnet 16 linearly reciprocates the piston 4 by a mutual electromagnetic force, thereby a refrigerant is sucked into the compression space P, and compressed and discharged.
The structure comprising the cylinder 2, the piston 4 and the linear motor 10 is installed in a shell (not shown) which is a hermetic space, and elastically supported by buffering springs (not shown). A suction valve 6 is installed on a suction hole 4h formed at one end of the piston 4 to communicate with the compression space P. A discharge valve assembly 8 in which a discharge valve 8a is elastically supported by a discharge valve spring 8c inside a discharge cap 8b to be opened and closed is installed at one end of the cylinder 2. Accordingly, suction and discharge of the refrigerant are controlled according to a pressure inside the compression space P.
One end of the cylinder 2 is fixed to the frame 20. The inner stator 12 is fixedly installed on the outer circumference of the cylinder 2. The outer stator 14 is bolt-fastened between the frame 20 and the motor cover 30 with an interval from the outer circumference of the inner stator 12. The permanent magnet 16 is installed between the inner stator 12 and the outer stator 14 with an interval, and connected to the other end of the piston 4.
A supporter (not shown) connected to the other end of the piston 4 is elastically supported in the notion direction by a plurality of springs (not shown) between the motor cover 30 and a main body cover (not shown) installed with an interval from the motor cover 30 in the motion direction.
Accordingly, the cylinder 2, the inner stator 12, the outer stator 14, the frame 20, the motor cover 30 and the main body cover are fixed, and the piston 4, the permanent magnet 16 and the supporter are linearly reciprocated. As the pressure inside the compression space P is varied, the refrigerant is sucked into the compression space P, compressed, and discharged.
As shown in FIG. 2, the frame 20 is formed in a flat plate shape. A cylinder mounting hole 24 through which the cylinder 2 is installed is formed at the frame 20. A motor terminal taking out hole 26 is formed at one side of the frame 20, so that a motor terminal (not shown) connected to a coil winding body (not shown) of the outer stator 14 can be taken out through the motor terminal taking out hole 26.
Since an interval between the frame 20 and the shell (not shown) is small, the motor terminal taking out hole 26 is formed on the side surface of the frame 20 to take out the motor terminal. Therefore, even if vibration is generated, this configuration prevents an electric wire connected to the motor terminal frame being damaged in contact with the shell (not shown) and the frame 20.
The portion around the motor terminal taking out hole 26 of the frame 20 is formed thick for stably supporting the outer stator 14, even though the motor terminal taking out hole 26 is formed at one side of the frame 20.
Except the surface 22 of the frame 20 for supporting the outer stator 14, an unnecessary portion of the frame 20 is removed to reduce the whole volume of the frame 20. In addition, four bolt holes 22h are formed on the frame 20 so that the motor cover 30 can be bolt-fastened to the frame 20. Accordingly, protruding units 22a and 22b are protruded from the frame 20 to secure spaces for forming the bolt holes 22h. 
Meanwhile, the motor cover 30 is formed in a metal plate shape. One surface 32 of the motor cover 30 supports the outer stator 14. Bolt holes 32h are formed on the motor cover 30 to correspond to the bolt holes 22h of the frame 20, so that the motor cover 30 can be bolt-fastened to the frame 20.
Preferably, a through hole 34 is formed at the center portion of the motor cover 30, so that the other end of the piston 4 can pass through the through hole 34 for linear reciprocation.
The frame 20 and the motor cover 30 are positioned on the same axle. The motor cover 30 is bolt-fastened to the frame 20 in the motion direction of the piston 4, for supporting and fixing the outer stator 14. The motor terminal is taken out through the motor terminal taking out hole 26 of the frame 20, and connected to a power supply source.
However, in the conventional mounting structure of the linear compressor, since the motor terminal taking out hole 26 is formed at one side of the frame 20 to take out the motor terminal, the frame 20 is not completely symmetric. When the motor cover 30 is bolt-fastened to the frame 20, twist deformation may occur due to the fastening force. Accordingly, the cylinder 2 installed between the frame 20 and the motor cover 30 may be deformed to cause an assembly error and an operation error. Furthermore, when the motor terminal taking out hole 26 is formed at the frame 20, the hole-formed portion of the frame 20 must be formed relatively thick to stably support the outer stator 16. As a result, the manufacturing process is complicated and the material cost is increased.